Modelling of daily fluxes of water and carbon from shortgrass steppes

A process-based model for semi-arid grassland ecosystems was developed. It is driven by standard daily meteorological data and simulates with a daily time step the seasonal course of root, aboveground green, and dead biomass. Water infiltration and redistribution in the soil, transpiration and evapo ration are simulated in a coupled water budget submodel. The main plant pro cesses are photosynthesis, allocation of assimilates between aboveground an d belowground compartments, shoots and roots respiration and senescence, an d litter fall. Structural parameters of the canopy such as fractional cover and LAI are also simulated. This model was validated in southwest Arizona on a semi-arid grassland site. In spite of simplifications inherent to the process-based modelling approac h, this model is useful for elucidating interactions between the shortgrass ecosystem and environmental variables, for interpreting H2O exchange measu rements, and for predicting the temporal variation of above- and belowgroun d biomass and the ecosystem carbon budget. Published by Elsevier Science B. V.